JPH02200479A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve sensitivity and shelf stability by incorporating a dihydroxy diphenyl ether shown by a specific formula and at least one of compounds selected from among groups consisting of 1,1-biscyclohexane and compounds shown by a specific formula in a thermal recording layer. CONSTITUTION:A dihydroxy diphenyl ether shown by a specific formula I is normally used in the amount of 0.5-3 pts.wt. per 1 pts.wt. of a color forming basic dye. At least one of compounds selected from among groups consisting of a color developer of 1,1-bis(hydroxyphenyl)cyclohexane and compounds shown by a specific formula II is added in the amount of 0.1-20 pts.wt. per 1 pts.wt. of said color developer. A recording layer forming method is not particularly limited; for example, an appropriate coater, such as an air knife coater and a blade coater, can be used in such a method as a heat-sensitive liquid is applied to a substrate. The thermal color-forming layer is normally applied in the range of 2-12g/m<2> in dry weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive recording material. In particular, it relates to a heat-sensitive recording material that is excellent in color development and other recording properties, and has good storage stability.

[Prior Art] Various types of heat-sensitive recording materials have been announced so far that utilize a heat-coloring reaction between at least one colorless or light-colored basic dye and phenols, organic acids, etc.
-14039, etc.) have been widely put into practical use. These heat-sensitive recording materials are used in a wide range of fields, including measurement recorders, computers and information communication terminals, facsimile machines, and automatic ticket vending machines. These recording devices are equipped with a thermal element such as a thermal head or a thermal pen, and by heating this element, color can be generated and a recording can be obtained. Recently, applications have become more diverse and equipment has become more sophisticated.
Along with this, the quality required for thermal recording paper is also becoming more advanced.For example, for facsimile, A4
What used to take several minutes to record a size can now be done in less than a minute.

Under these circumstances, adding a sensitizer has been proposed as a method to improve the sensitivity of thermal recording paper, but this method has problems with color development sensitivity, color image stability, recording suitability,
A material that satisfies the well-balanced performance required for a heat-sensitive recording material has not yet been obtained.

In heat-sensitive recording paper, a color-forming substance and a phenol compound are present in the heat-sensitive recording layer as finely dispersed particles, and it is thought that upon heating, one or both of them will dissolve and come into close contact with each other, producing color. ing.

As a suitable phenol compound to be used for this purpose, 22-bis(4
'-Hydroxyphenyl)propane (bisphenol A
, M point 156°C) is widely used (for example, U.S. Pat. No. 3,539,375). However, this bisphenol A has poor thermal responsiveness, and as thermal recording paper becomes faster and smaller as thermal recording devices become faster and smaller, bisphenol A is widely used. It has not always been possible to satisfy market demands for higher sensitivity. Many sensitizers have been proposed to compensate for this drawback, including waxes (Japanese Patent Application Laid-Open No. 19231-1982) and phthalate esters (Japanese Patent Application Laid-open Nos. 116690-1982 and 58-1982). -98285), benzyl phenyl ether derivatives (JP-A-59-155096), benzylphenyl ether derivatives (JP-A-80-82382), naphthol derivatives (JP-A-80-82382),
JP-A No. 58-87094) and carbonic acid diesters (JP-A No. 58-138489) have been proposed, but when combined with the above bisphenol A, they are not sufficient in terms of whiteness, color development sensitivity, fog, etc. Moreover, in JP-A-56-144193, benzyl p-hydroxybenzoate or methylbenzyl p-hydroxybenzoate is used as a color developer to increase the sensitivity of heat-sensitive recording sheets. Although this method has been proposed, there is a problem with its storage stability because the coloring part turns white (powdering) during record storage.

As described above, the current state of the art is that it has not been possible to sufficiently meet the high quality demands of the market, including color development properties and storage stability.

The present inventors discovered that by using dihydroxydiphenyl ether represented by the formula above as a color developer, it is possible to provide a heat-sensitive recording material with high sensitivity and high whiteness, and filed an application (Japanese Patent Application No. 63-4498 issue). However, this substance tends to have insufficient storage stability.

For example, if thermal paper is left for 24 hours in an atmosphere of 60'Cl2O%RH or 40°C and 90%RH, the recording density may decrease and the residual rate may be less than 80%. Ta.

Therefore, the present inventors conducted extensive research in order to obtain a heat-sensitive recording material with high sensitivity and excellent storage stability, and found that 1.
1.3-1 Lis(2-methyl-4-hydroxy-5-t
-butylphenyl)butane, 1.1.3-1 lis(2-
Methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1.3.5-1lis(4-t-butyl-3-
hydroxy-2,6-dimethylbenzyl)incyanuric acid, and 1,1-bis(2-methyl-4-hydroxy-
High sensitivity can be achieved by using one or more compounds selected from the group consisting of (5-t-butylphenyl)butane in combination with a color developer consisting of dihydroxydiphenyl ether represented by the above general formula. We have discovered that this technology provides high whiteness and excellent storage stability, and have filed Japanese Patent Application No. 187338/1983).

[Problems to be Solved by the Invention] The object of the present invention is to provide a heat-sensitive recording material that exhibits even higher sensitivity than the heat-sensitive recording material of the above-mentioned Japanese Patent Application No. 187338/1982, and has even better durability. That is.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventors conducted intensive research and found that a compound consisting of 1.1-bis(4-hydroxyphenyl)cyclohexane and a compound represented by the general formula It has been found that 111 or more compounds selected from the group can be used to obtain heat-sensitive recording materials of the general formula.

Examples of dihydroxydiphenyl ether having the general formula include 2.2°-dihydroxydiphenyl ether (melting point 121°C), 3.3°-dihydroxydiphenyl ether (melting point 98°C), and 4.4°-dihydroxydiphenyl ether (melting point 166°C). can.

1. 1-Bis(4-hydroxyphenyl)cyclohexane (melting point 180°C), when used in combination with a color developer consisting of dihydroxydiphenyl ether cica), provides superior shelf life and also has the above-mentioned characteristics. Gansho 63-18733
It is a compound which has higher sensitivity than the heat-sensitive recording material according to No.
(corresponding to No. 75) and Japanese Patent Application Laid-Open No. 155059/1983.

The compound represented by the general formula is 4.4'-(ring-)unisene diisopylidene)bisphenol (melting point 141°C)
There is
No. 25790, JP-A No. 60-228189 and JP-A No. 6
No. 0-248395.

In the present invention, 0.5 to 3 parts by weight of dihydroxydiphenyl ether is usually used per 1 part by weight of the color-forming basic dye, and 1.1 parts by weight of the color developer is used per 1 part by weight of the same color developer.
One or more compounds selected from the group consisting of bis(4-droxyphenyl)cyclohexane and a compound represented by the general formula are added in an amount of 0.1 to 20 parts by weight. Preferably, 1 to 2 parts by weight of dihydroxydiphenyl ether is used per 1 part by weight of the color-forming basic dye, and 1.1-bis(
It is preferable to add 0.2 to 5 parts by weight of a compound of 1aI or higher selected from the group consisting of 4-hydroxyphenyl)cyclohexane and a compound represented by the general formula.

This greatly increases storage stability, such as dihydroxydiphenyl ether, 1,1-bis(4-droxyphenyl)cyclohexane, or the general formula (H
Compared to the case where each of the compounds represented by 1 was used alone, the recording density retention rate was improved by 10 to 20%, and not only did it reach a level that poses no problem in practice, but the sensitivity was also improved when each compound was used alone. Comparatively, there was a huge improvement.

From this, it is clear that there is some kind of interaction between the two color developers, but it is not necessarily clear what mechanism is involved in the interaction to improve storage stability and sensitivity.

In addition, 2,2-bis (4°
-Hydroxyphenyl)propane or benzyl p-hydroxybenzoate in combination with the above two types of color developers had poor sensitivity and storage stability improvement effects, and lacked beneficial effects due to interaction.

As the colorless or light-colored basic leuco dye used to form the heat-sensitive recording layer in the present invention, for example, the following can be used.

For example, basic dyes include triallylmethane dyes such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-diethylamino-6-
Methyl-7-phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane,
3-(N-cyclohexyl-N-methylaminone-6-
Methyl-7-phenylaminofluoranmino-7-(o-lylorophenylamino)fluoran,
Examples include 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluoran.

Furthermore, in heat-sensitive recording materials, there is no problem in using a combination of auxiliary substances that can generally be added.
For example, as a sensitizer, parabenzylphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-0-lylorbenzyl adipate, 1,2-di(3-methylphenoxy)ethane, sulfur Di-p-chlorobenzyl acid and the like can be used.

In the heat-sensitive recording material of the present invention, any support material may be used to form the heat-sensitive coloring layer. for example,
Paper, synthetic fiber paper, synthetic resin film, etc. can be used as appropriate. Paper is generally preferred.

To prepare a coating solution for forming a heat-sensitive coloring layer, water is used as a dispersion medium, and the dye, dihydroxydiphenyl ether, and preservability-improving substance are dispersed using a grinder such as a ball mill, attritor, or sand grinder to form a coating solution.
Such coating fluids contain binders such as starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, maleic anhydride copolymer salt, styrene-butadiene copolymer emulsion, etc. It is used in an amount of 2 to 40% by weight, preferably 5 to 25% by weight of the total solid content. Various auxiliary materials may be added to the coating liquid as necessary. For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, antifoaming agents, fluorescent dyes, color dyes, etc. can all be added. In addition, to further whiten the heat-sensitive recording layer, kaolin, clay, talc,
Inorganic pigments such as calcium carbonate, calcined resin, titanium oxide, diatomaceous earth, and particulate anhydrous silica may also be added. Stearic acid, polyethylene, carnauba wax, as appropriate.
A wax head such as a dispersion or emulsion of paraffin wax, calcium stearate, zinc stearate, ester wax, etc. can also be added as required.

In the heat-sensitive recording material of the present invention, the method of forming the recording layer is not particularly limited. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater can be used.

The thermosensitive coloring layer is generally formed to have a dry weight of 2 to 12 g/m, preferably 3 to 89 g/m''.

Note that there is no problem in making various known modifications such as providing an undercoat layer as necessary.

[Examples] Examples of the present invention are shown below, but the present invention is not particularly limited by these. Parts and % in the Examples and Comparative Examples indicate parts by weight and % by weight.

Example 1 (2) Preparation of Part A 10% polyvinyl alcohol aqueous solution 20 parts Water 20 parts This composition was ground to an average particle size of 1 μm using a sand grinder.

■ Preparation of B solution 4.4°-dihydroxydiphenyl ether 40 parts 1
0% polyvinyl alcohol aqueous solution 20 parts water
20 parts of this composition were ground in a sand grinder to an average particle size of 1.5 microns.

■ Liquid C preparation rosebenzyl biphenyl 40 parts 10%
Polyvinyl alcohol aqueous solution 20 parts water
20 parts of this composition were ground in a sand grinder to an average particle size of 1.5 microns.

■ Solution D preparation 10% polyvinyl alcohol aqueous solution 20 parts water
20 parts of this composition were ground in a sand grinder to an average particle size of 1.5 microns.

10 parts of liquid A, 20 parts of liquid B, 20 parts of liquid C, 10 parts of liquid D, 5
75 parts of a 10% polyvinyl alcohol aqueous solution was added to 30 parts of a 0% calcium carbonate dispersion and 8 parts of a 30% zinc stearate dispersion, and the mixture was stirred to obtain a coating liquid. 50% of this coating liquid
A heat-sensitive recording paper was obtained by coating and drying the mixture on a base paper of y/s" so that the coating weight after drying was 7 y/w".

Example 2 A thermal recording paper was obtained in the same manner as in Example 1 except that 20 parts of liquid B in Example 1 was changed to 10 parts and 10 parts of liquid D was changed to 20 parts.

Example 3 The same procedure as in Example 1 was carried out except that 1.1-bis(4-hydroxyphenyl)cyclohexane in Solution B was replaced with 4.4°-(phenylenediisopropylidene)bisphenol. A thermosensitive recording paper was obtained.

Example 4 The same procedure as in Example 1 was carried out except that 1.1-bis(4-hydroxyphenyl)cyclohexane in Solution B was replaced with 4.4"-(p-phenylenediisopropylidene)bisphenol. A thermosensitive recording paper was obtained.

Comparative Example I A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 30 parts of Liquid D was used instead of Liquid B.

Comparative Example 2 A thermal recording paper was obtained in the same manner as in Example 1, except that 30 parts of Liquid B was used instead of Liquid D.

Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that the dispersion used in Example 3 was used instead of Liquid D in Comparative Example 1.

Comparative Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that the dispersion used in Example 4 was used instead of Liquid D in Comparative Example 1.

The eight types of heat-sensitive recording papers obtained in this way were subjected to super calender finishing, and UF
After printing at -60, the recorded density was measured using a Macbeth RD-100R type densitometer.

Furthermore, a storage stability test was conducted using the printed matter obtained in the recording density test, and the residual rate of recording density was calculated using the following formula.

However, for the heat resistance test, the printed matter was left in an atmosphere of 60°C and 20% RH for 24 hours, and for the moisture resistance test, the printed matter was left at 40°C.
After being left for 24 hours in an atmosphere with a RH of 90%, the recording density was measured.

[Effects of the Invention] According to the present invention, it was possible to provide a heat-sensitive recording material which has higher color development sensitivity and which can be used in a wide range of practical applications required for heat-sensitive recording materials, and which has better storage stability.

Patent applicant: Oji Paper Co., Ltd. (one other person) As is clear from the table, the heat-sensitive recording material according to the present invention has four
．． Due to the interaction caused by the inclusion of 4°-dihydroxydiphenyl ether and 1,1-bis(4-hydroxyphenyl)cyclohexane, recording density and storage stability are improved compared to when each of the comparative examples is used alone. It's extremely good.

Continuation of the procedure Correction book

Claims (1)

[Scope of Claims] In a heat-sensitive recording material that utilizes a color-forming reaction between at least one basic dye and a color developer capable of forming a color when it comes into contact with the basic dye, the heat-sensitive recording layer contains the formula ▲ , chemical formulas, tables, etc. ▼ Dihydroxydiphenyl ether represented by (I) and 1,
1-bis(4-hydroxyphenyl)cyclohexane and one or more compounds selected from the group consisting of the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (II) A heat-sensitive recording material characterized by: